What makes speakers "disappear " and can it be measured?

[Holmz]

I really doubt that putting some felt on the front facia of a speaker in a rectangle (Dunlavy) or sawtooth (Wilson Audio) pattern will produce good spinorama results compared to a speaker with a waveguide. The built also looks very cheap to me, especially the Dunlavy speaker.

Well…Can that be backed up in any way?

I was driving down the road the other day.
In the US most curbing at the roadside is a rectangular;at section, and the driveways have a ramp.
In Australia a lot of curbing is ramped, especially roundabouts (Traffic circles).
Whether it is the curbing or signs, even time I go past one the noise in an open wind modulates up and down, as the curbing is a corner reflector.
It gets to the point that Hellen Keller could almost drive the car, or at least count the number of driveways.

Anyhow as the wave launches to the side it either falls of the edge of the baffle or it hits a mismatch and get diffracted… or some of both.
I am not sure exactly how the felt works. Part of me would like to defer to the Michelson Morley double slot, but the acoustic wave is not a quantum effect and it is not particle.
I would also like to be leave that the felt may slow down the speed of sound, similar to how a dielectric slows down an E field… and therefore (if it did), it could be doing some impedance matching function. In general that could help stick the wave to the surface.
And the zig-zag pattern would/could be causing the diffraction of be more diffuse, similar to the stupid looking surround on a purify driver… Whic hdoes not look too stupid if one considers function. It then starts to look pretty smart.

If the speaker was a bat, and the edge of the cabinet an insect, then it get apparent that at a lot of frequencies that the insect if in the Mie scatter region, rather than the Rayleigh region. Those “reflections” would be making the edge of the speaker a source of sound. So now we have a driver, and say the left and right edge.
We could certainly be better to have say a membrane like an electrostatic or magnetically driven panel where the whole membrane is the “driver” and the surround is NOT moving, but have a boundary condition when the displacement is zero.

There is no great statement happening ^here^, only that there is potentially some interesting stuff happening that I have not gotten my head aroun, and I am not a acoustics fellow, so I would certainly defer and like to know the science.
But the felt seems like it could be doing something to that wave.

 

[pablolie]

The ability of speakers to "disappear" is about positioning of the speakers to optimally interact with the particular real-world room, and if that doesn't magically happen, room correction/optimization with DSP helps (highly recommended these days anyhow).

The measurements we see are single speaker measurements, so no, they don't tell us much about a speaker's ability to disappear, but my running assumption is all competently designed speakers have that ability if positioned/corrected capably.

 

[ahofer]

Isn't this basically one aspect of the "soundstage" discussion?

 

[Pearljam5000]

Isn't this basically one aspect of the "soundstage" discussion?

I'm not sure they're the same thing
But I could be wrong obviously

 

[Newman]

Ah, there you go. I forgot about that monstrosity for a moment.

That is not actually coaxial, any more than a D'Appolito is coaxial.

 

[Pearljam5000]

That is not actually coaxial, any more than a D'Appolito is coaxial.

How's that not a coaxial?

 

[Newman]

I thought they were talking about the speaker being coaxial.

 

[terryforsythe]

Earlier this year I spent much time working on my speakers, Elac UBR62 UniFi Reference. I found that reducing the harmonic distortion helped to make the speakers disappear.

Out of the box the harmonic distortion was a bit high between about 180Hz and 400Hz, peaking around -32dB at 86dB SPL and -28dB at 96 SPL.. Attached are measurements from Erin's Audio Corner. My initial measurements were similar.

Also attached is my frequency response and harmonic distortion after the modifications. I measured it at my listening position, a little over 3m from the speaker, with a lot of PEQ for room correction. SPL at 1m is around 10dB higher than the measurement at the listening position.

The subwoofer is handling everything below 100Hz. The harmonic distortion below 35 Hz is not completely accurate - my walls, and things on my walls, vibrate when I run the frequency sweeps, adding to the harmonic distortion down low.

 

[Brent71]

But Wilson Audio does the same thing
So how's that possible? View attachment 392813

Because patents only last for so long? A lot of speaker companies copied John Dunlavy, AR is one that comes to mind immediately.

 

[Brent71]

I really doubt that putting some felt on the front facia of a speaker in a rectangle (Dunlavy) or sawtooth (Wilson Audio) pattern will produce good spinorama results compared to a speaker with a waveguide. The built also looks very cheap to me, especially the Dunlavy speaker.

Remember, you're talking about designs that are 20 - 30 years old now. JD could have built fancy cabinets, but he chose what worked and was a reasonable cost. I have yet to see any passive speaker, at any price, match their impulse response, step response and frequency response measurements to this day; they're just about textbook perfect. To make an accurate passive speaker you have to have: 1) stepped baffles, 2) sealed enclosures, 3) 1st-order crossovers, very few speakers have all 3.

 

[Thomas_A]

Remember, you're talking about designs that are 20 - 30 years old now. JD could have built fancy cabinets, but he chose what worked and was a reasonable cost. I have yet to see any passive speaker, at any price, match their impulse response, step response and frequency response measurements to this day; they're just about textbook perfect. To make an accurate passive speaker you have to have: 1) stepped baffles, 2) sealed enclosures, 3) 1st-order crossovers, very few speakers have all 3.

Ino Audio's bigger models? Been around for a long time, but hardly known by people outside Sweden. Picture shows one of the larger "monitors" that are designed to go with subs. 4x9-inch woofers playing from 80 Hz and up.

 

[terryforsythe]

Because patents only last for so long?

Correct. The patent in the link expired in 1996. Since then, the invention has been available for anyone to use. Essentially, a patent is an agreement between the patentee and the government - "if you give me the patent rights for a limited time, after that time expires I donate the patented technology for the public good",

 

[Brent71]

Ino Audio's bigger models? Been around for a long time, but hardly known by people outside Sweden. Picture shows one of the larger "monitors" that are designed to go with subs. 4x9-inch woofers playing from 80 Hz and up.

Never seen or heard of those before. Seems odd to jump from a 1-inch tweeter to 9-inch woofers, there's going to be a big difference in beam-width at the crossover point; very narrow for the woofers, very wide for the tweeter. John Atkinson brought up this very topic in the John Dunlavy interview too.

Atkinson: I do wonder that with designers who haven't thought through the fundamentals of what they're trying to achieve in loudspeaker design, a lot of the tweaking or "voicing" that they do with their speakers is balancing problems in the on-axis response, say, with those in the power response, or vice versa. Let's imagine that someone is using an 8" midrange unit that beams quite narrowly at the top of its passband, crossing over to a 1" tweeter that has very wide dispersion at the bottom of its passband. That speaker will tend to sound bright. So what the designer then does is to pull down the on-axis response in the presence region—he ends up fudging both the on-axis response and the power response to get something that will sound flat in a typical room. But you don't have a loudspeaker that is in any way accurate. And certainly you don't have any accuracy in the time domain. The step response will be all over the place.
Dunlavy: That's a very good observation, and certainly very, very true.

2 pages later:

Atkinson: All the Dunlavy Audio Labs Signature loudspeakers feature a vertically symmetrical array of drive-units. Does that come about because of an analogy with antenna design?
Dunlavy: Yes, it does. In an antenna, generally you want the beam tailored so you get the energy directed in a certain direction to achieve maximum efficiency. Similarly, if you want a speaker to have a fairly flat room response, you can only achieve that by tailoring the design of the speaker such that the separation of the various drivers, as expressed in wavelengths across the audio spectrum, maintains a more or less constant vertical beam-width as well a fairly constant horizontal beam-width. That comes about by choosing drivers of different diameters. Say you have a 15" woofer, and you measured the beamwidth at 1kHz, then you compared that with, say, a 4" midrange at the same frequency. Good heavens—no comparison. A 4" midrange will have a very broad beam; the 15" woofer will have a very narrow beamwidth—you can find it by dividing 57 by the dimension expressed in wavelengths. That's the beamwidth.

You want symmetrical coupling into the room, which then implies symmetrical radiation patterns from the speaker in both horizontal and vertical planes. To achieve that, you have to have a symmetrical driver array. You place the tweeter at the average height of a seated listener's ears, which we take to be between 37" and 40", depending on the person in the chair. Then the rest of the drivers—a pair of midranges and a pair of woofers, or whatever—are symmetrically arranged above and below that tweeter.

 

[Thomas_A]

Never seen or heard of those before. Seems odd to jump from a 1-inch tweeter to 9-inch woofers, there's going to be a big difference in beam-width at the crossover point; very narrow for the woofers, very wide for the tweeter. John Atkinson brought up this very topic in the John Dunlavy interview too.


2 pages later:

The first speakers were designed around 1979 or perhaps beginning of 1980s. They measure and sound good IMO especially the larger models I’ve listened to. Below a link to the smallest base model. Perhaps not text-book linear response but within +/- 2 dB or so. Tweeters have both waveguides and felt.

Stereo systems_2

 

[Holmz]

The first speakers were designed around 1979 or perhaps beginning of 1980s. They measure and sound good IMO especially the larger models I’ve listened to. Below a link to the smallest base model. Perhaps not text-book linear response but within +/- 2 dB or so. Tweeters have both waveguides and felt.

Stereo systems_2

That pulse response in the link, is stunning.
Tack!/Tak!

I know that it is “frequency response uber alles” here.
At some point the time domain behaviour matters. These seem to have it.

 

[Pearljam5000]

So basically
Are there any specific speakers that that can be defined as the best at disappearing?

 

[IPunchCholla]

So basically
Are there any specific speakers that that can be defined as the best at disappearing?

Any PA system at a concert? They may not sound great, but my brain is pretty convinced the sound is coming from the folks on stage.

 

[Count Arthur]

So basically
Are there any specific speakers that that can be defined as the best at disappearing?

 

[dualazmak]

That pulse response in the link, is stunning.
Tack!/Tak!

I know that it is “frequency response uber alles” here.
At some point the time domain behaviour matters. These seem to have it.

Yes, I fully agree with you.

At least in my case, I intensively did it (= what you mean) over all the SP drives i.e. subwoofers, woofers, midranges, tweeters, and super-tweeters, using 8-wave 3-wave one-wave rectangular sine-tone pulse/burst in various frequencies.

Using the "time-shifted" 8-wave rectangular tone burst sequences, I could establish 1 ms precision time-alignment between sub-woofers and other SP drivers, and furthermore using 3-wave tone bursts I could establish 0.1 ms precision time-alignment between woofer and midrange+tweeter+super-tweeter.

I also objectively measured/observed that my 30 cm woofer in heavy-rigid-"sealed"-cabinet directly (eliminating passive crossover network) driven by HiFi amplifier with excellent damping factor gives not only nice kick-up response but also unexpectedly excellent fade-out/extinction behavior after the rectangular pulse stimulation even at the low 45 Hz.

Spoiler

- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-1_ Precision (time-shifted) pulse wave matching method: #493
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-2_ Energy peak matching method: #494
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-3_ Precision single sine wave matching method in 0.1 msec accuracy: #504, #507
- Measurement of transient characteristics of Yamaha 30 cm woofer JA-3058 in sealed cabinet and Yamaha active sub-woofer YST-SW1000: #495, #497, #503, #507
- Identification of sound reflecting plane/wall by strong excitation of SP unit and room acoustics: #498

These pulse wave stimulation and wave-shape measurements/analysis of the recorded air sound were/are very much useful in optimization of XO configuration (filter type, XO Fq, relative-gains, slopes, phase-inversion or not, group-delay, etc.) not only between sub-woofer and woofer, but also among all the SP drivers driven directly by each of the dedicated amplifiers in PC-based-DSP multichannel multi-amplifier audio system, and hence greatly contribute to better/optimal "disappearance" of SPs.

Of course, the possible "disappearance" of SPs is greatly dependent on our individual room acoustic modes/environments, as I shared in my posts;
- Perfect (0.1 msec precision) time alignment of all the SP drivers greatly contributes to amazing disappearance of SPs, tightness and cleanliness of the sound, and superior 3D sound stage: #520
- Not only the precision (0.1 msec level) time alignment over all the SP drivers but also SP facing directions and sound-deadening space behind the SPs plus behind our listening position would be critically important for effective (perfect?) disappearance of speakers: #687

You would please find details of my latest audio setup, well covering all of the above mentioned topics, in my post here #931 on my project thread.
- The latest system setup of my DSP-based multichannel multi-SP-driver multi-amplifier fully active audio rig, including updated startup/ignition sequences and shutdown sequences: as of June 26, 2024: #931

 

[Thomas_A]

That pulse response in the link, is stunning.
Tack!/Tak!

I know that it is “frequency response uber alles” here.
At some point the time domain behaviour matters. These seem to have it.

To add, the designer does not really say that this is a crucial property. In the frequency range of 200-2000 Hz there may be, during certain circumstances, audible difference. And he adds that other aspects of the speaker out such as frequency response and distortion is much more important.

(I reread his documents and the first pi60 speaker came 1978. The designer, Ingvar Öhman, was at that time 16 years old.)